1. Field of the Invention
The present invention generally relates to orthodontic appliances and more particularly to an orthodontic chain elastic having varying inter-aperture spacing and regions having differing cross sections resulting in varying force levels along the length thereof.
2. Description of Related Art
It is known to use chain elastic or power chain to close spaces between teeth in orthodontic applications. Conventional chain elastic is generally uniform in construction and sold in 15-foot lengths. Three formats are offered that are commonly called continuous, short and long formats which indicates the uniform distance between the holes in the chain. Each format has a uniform force based upon a uniform thickness and construction of the device. When stretched distances as presented from hole to hole in the chain are equivalent. The continuous format is used to apply high closing forces, the short format is used to apply medium closing forces, and the long format is used to apply weaker closing forces.
The teeth in the mouth vary in the amount of root surface that is embedded in the gingiva or gums. Because the root surface area varies, the amount of force needed to move the various teeth differs. In addition, the spacing between the brackets affixed to the various teeth is not uniform. The generally uniform construction and spacing of conventional chain elastic limits its use as it cannot be easily adapted to meet the needs of the orthodontist confronted with patients having teeth of varying root surface and varying inter-bracket distances. Also it is common that bracket sizes for lower and anterior teeth are smaller that bracket sizes for upper and posterior teeth.
The use of the chain elastic having a generally uniform construction is further limited in that the elastic material may fail if it is stretched beyond its elastic limit. Such a condition may occur in attempting to bridge a large inter-bracket distance.
There is a need in the art for an orthodontic chain elastic that overcomes these limitations of the prior art. The orthodontic chain elastic is preferably capable of applying varying amounts of force to teeth having different amounts of root surface. The orthodontic chain elastic is also preferably configured to accommodate varying inter-bracket distances.